1. Field of the Invention
This invention relates to a plug, a sound inputting and outputting apparatus and a noise cancel system, and more particularly to a plug of a five-pole configuration and a sound inputting and outputting apparatus and a noise cancel system in which a plug of a five-pole configuration is used.
2. Description of the Related Art
A plug to be connected to a jack of various electronic equipments such as, for example, an acoustic equipment is provided at an end portion of, for example, an earphone, a headphone, or various connection cables.
Generally, such a plug as described above such as, for example, a plug provided on an earphone, a headphone or the like, has a three-pole configuration for a speaker L (left), a speaker R (right) and the ground as disclosed, for example, in Japanese Patent Laid-Open No. Hei 9-204966 (hereinafter referred to as Patent Document 1).
A sound inputting and outputting apparatus such as an earphone or a headphone in which such a plug as described above is provided includes a pair of auricle mounting portions for being mounted on a pair of auricles of a user. However, when sound is outputted from a pair of speakers of the sound inputting and outputting apparatus in a state wherein the auricle mounting portions are mounted on the auricles of the user, such a disadvantage sometimes occurs that external sound is inputted as noise to the auricles depending upon the external environment or the like.
Countermeasures for canceling such noise are available in the related art. According to one of the related art, a microphone and a circuit board on which a noise cancel circuit is formed are disposed in each of the auricle mounting portions of the sound inputting and outputting apparatus. The noise cancel circuit produces a noise cancel signal based on a noise signal inputted to the microphone, and the noise cancel signal is outputted from the speaker provided in each of the auricle mounting portions to cancel the noise.